1. Field of the Invention
The present invention relates to a film adopted for use in an intermediate image transfer member, which may be used in the form of an endless belt, to which a toner image can be transferred, and which is capable of reducing the formation of image transfer dust and the deposition of toner on the background of images in an image formation process.
The present invention also relates to an endless-belt-shaped film made of the above-mentioned film for use in the intermediate image transfer member.
2. Discussion of Background
Conventionally, there is known an image formation apparatus in which a latent electrostatic image is formed on a latent image bearing member such as a photoconductor drum, the latent electrostatic image is developed with toner to a visible toner image, the visible toner image is then electrostatically transferred to an endless-belt-shaped intermediate image transfer belt, and the toner image is further transferred from the intermediate image transfer belt to a recording material such as a transfer sheet.
In this kind of image formation apparatus, an electroconductive intermediate image transfer belt is widely used as the above-mentioned intermediate image transfer belt.
However, it is difficult to set the surface resistivity or the electroconductive intermediate image transfer belt at an appropriate value. For example, in Japanese Patent 2560727, it is described that proper images can be formed when the surface resistivity of the electroconductive image transfer image transfer belt is in a range of 107 to 1015 [Ω/□]. However, there is a case where the deposition of toner on the background of images occurs and image transfer dust is formed, with a toner being transferred away from its right image transfer position even when the surface resistivity of the electroconductive image transfer belt is set in the above-mentioned range. It is also known that such image transfer dust occurs frequently when an intermediate image transfer belt with lower surface resistivity is used. Such image transfer dust is considered to be caused by the electric lines of force, formed between the intermediate image transfer belt and the latent electrostatic image bearing member, being disturbed in the direction of the surface of the intermediate image transfer belt. Furthermore, it is known that the deposition of toner on the background of images occurs frequently when an intermediate image transfer belt with higher surface resistivity is used. Thus, there is a dilemma in which when the surface resistivity of the intermediate image transfer belt is increased in order to reduce the formation of the image transfer dust, the deposition of toner on the background of images is increased, while when the surface resistivity of the intermediate image transfer belt is decreased in order to reduce the deposition of toner on the background of images, the occurrence of the image transfer dust is promoted.
In order to get out from such a dilemma, it will be necessary to set the surface resistivity of the intermediate image transfer belt at a high surface resistivity and also to provide a charge quenching unit for quenching electric charges of the intermediate image transfer belt. However, the provision of such a charge quenching unit not only makes the image formation apparatus costly, but also makes the mechanism of the image formation apparatus complex. Therefore, the provision of the quenching apparatus is not a preferable step from the above point of view. Furthermore, a corona charger, which is one of the simplest quenching apparatus, is considered to be usable for the above-mentioned purpose. However, the corona charge has a shortcoming that it generates ozone and causes an air pollution problem.